Fully relativistic complete active space self-consistent field for large molecules: Quasi-second-order minimax optimization

Journal Article · Wed Jan 28 00:00:00 EST 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4906344· OSTI ID:22416038

Bates, Jefferson E.; Shiozaki, Toru ^[1]

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1. Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208 (United States)

We develop an efficient algorithm for four-component complete active space self-consistent field (CASSCF) methods on the basis of the Dirac equation that takes into account spin–orbit and other relativistic effects self-consistently. Orbitals are optimized using a trust-region quasi-Newton method with Hessian updates so that energies are minimized with respect to rotations among electronic orbitals and maximized with respect to rotations between electronic and positronic orbitals. Utilizing density fitting and parallel computation, we demonstrate that Dirac–Coulomb CASSCF calculations can be routinely performed on systems with 100 atoms and a few heavy-elements. The convergence behavior and wall times for octachloridodirhenate(III) and a tungsten methylidene complex are presented. In addition, the excitation energies of octachloridodirhenate(III) are reported using a state-averaged variant.

• OSTI ID: 22416038
• Journal Information: Journal of Chemical Physics, Vol. 142, Issue 4; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALGORITHMS
ATOMS
CONVERGENCE
DIRAC EQUATION
EXCITATION
L-S COUPLING
MOLECULES
NEWTON METHOD
OPTIMIZATION
ORGANIC CHLORINE COMPOUNDS
RELATIVISTIC RANGE
RHENATES
ROTATION
SELF-CONSISTENT FIELD
SPACE
TUNGSTEN